Instruments, systems and methods for sealing tissue structures

ABSTRACT

A method of sealing bowel tissue includes grasping bowel tissue between first and second electrically-conductive surfaces, applying a clamping pressure to the grasped bowel tissue in a range of about 1 kg/cm 2  to about 2.5 kg/cm 2 , supplying energy to at least one of the first and second electrically-conductive surfaces such that the energy is conducted between the first and second electrically-conductive surfaces and through the grasped bowel tissue to seal the grasped bowel tissue, and monitoring one or more parameters during the supplying of energy to the electrically-conductive surface(s). Instruments, end effector assemblies, generators, and systems suitable for this purpose are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 14/017,572, filed on Sep. 4, 2013, now U.S. Pat.No. 9,433,461, which claims the benefit of, and priority to, U.S.Provisional Patent Application No. 61/698,270, filed on Sep. 7, 2012,the entire contents of each of which are hereby incorporated byreference herein.

BACKGROUND

Technical Field

The present disclosure relates to surgical instruments, systems, andmethods. More particularly, the present disclosure relates to surgicalinstruments, systems, and methods for sealing tissue structures such asbowel (intestine) tissue or other similar tissue structures.

Description of Related Art

Approximately 2.5 million bowel fusion or anastomosis procedures areperformed worldwide each year. Fusion and anastomosis of the bowel hastraditionally been accomplished using sutures and/or staples.

Energy-based surgical instruments and systems, as an alternative or inaddition to suturing and/or stapling, utilize both mechanical clampingaction and energy, e.g., radiofrequency (RF) energy, to affecthemostasis by heating tissue to coagulate and/or cauterize tissue.Certain surgical procedures require more than simplycoagulating/cauterizing tissue and rely on the unique combination ofclamping pressure, precise energy control, and/or gap distance betweensealing surfaces to “seal” tissue. Depending on the particular tissuestructure to be sealed, the optimal parameters, e.g., clamping pressure,precise energy control, and/or gap distance, may vary.

SUMMARY

A method of sealing bowel tissue (or other similar tissue structures)provided in accordance with the present disclosure includes graspingbowel tissue between first and second electrically-conductive surfaces,applying a clamping pressure to the grasped bowel tissue in a range ofabout 1 kg/cm² to about 2.5 kg/cm², supplying energy to the first and/orsecond electrically-conductive surface such that the energy is conductedbetween the surfaces and through the grasped bowel tissue to seal thegrasped bowel tissue, and monitoring one or more parameters during thesupplying of energy to the surface(s). The one or more parameters may bebowel tissue temperature, bowel tissue impedance, an optical property ofbowel tissue, and/or sealing time.

With regard to bowel tissue temperature, the method may includecontrolling the supply of energy to the surface(s) to maintain the boweltissue temperature between a lower temperature limit and an uppertemperature limit. More specifically, the lower temperature limit maycorrespond to the minimum bowel tissue temperature for sealing boweltissue, while the upper temperature limit may correspond to the maximumbowel tissue temperature prior to occurrence of bowel tissuedenaturation, bowel tissue damage, and/or breakdown of bowel tissuelayer architecture.

With regard to bowel tissue impedance, the method may includecontrolling the supply of energy to the surface(s) to maintain a targetimpedance ramp, e.g., about 0.010 Ω/ms, and/or supplying energy to thesurface(s) until bowel tissue impedance reaches a target end impedance,e.g., about 200Ω.

With regard to one or more optical properties of bowel tissue, themethod may include supplying energy to the surface(s) until the opticalproperty of bowel tissue indicates bowel tissue denaturation, boweltissue damage, and/or breakdown of bowel tissue layer architecture.

With regard to sealing time, the method may include supplying energy tothe surface(s) for a sealing time of between about 18 and 22 seconds.

Another method of sealing bowel tissue provided in accordance with thepresent disclosure includes grasping bowel tissue with an appliedclamping pressure in a range of about 1 kg/cm² to about 2.5 kg/cm²,supplying energy to the grasped bowel tissue, and controlling the supplyof energy to the grasped bowel tissue such that the grasped bowel tissueis sufficiently sealed with minimal bowel tissue denaturation, boweltissue damage, and breakdown of bowel tissue layer architecture.Controlling the supply of energy includes monitoring one or moreparameters and providing control based on the one or more parameters.

In one aspect of the present disclosure, the parameter is bowel tissuetemperature and controlling the supply of energy includes maintainingthe bowel tissue temperature between a lower temperature limit,corresponding to the minimum bowel tissue temperature for sealing boweltissue, and an upper temperature limit, corresponding to the maximumbowel tissue temperature prior to occurrence of at least one of boweltissue denaturation, bowel tissue damage, and breakdown of bowel tissuelayer architecture.

In another aspect of the present disclosure, the parameter is boweltissue impedance and controlling the supply of energy includesmaintaining a target impedance ramp, e.g., about 0.010 Ω/ms, and/orsupplying energy until bowel tissue impedance reaches a target endimpedance, e.g., about 200Ω.

In still yet another aspect of the present disclosure, the parameter isan optical property of bowel tissue and controlling the supply of energyincludes supplying energy until the optical property of bowel tissueindicates bowel tissue denaturation, bowel tissue damage, and/orbreakdown of bowel tissue layer architecture.

Also provided in accordance with the present disclosure are instruments,end effector assemblies, generators, and systems suitable for use inaccordance with the above-detailed methods.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and features of the present disclosure are describedherein with reference to the drawings wherein like reference numeralsidentify similar or identical elements:

FIG. 1A is a perspective view of a surgical instrument provided inaccordance with the present disclosure;

FIG. 1B is a perspective view of another surgical instrument provided inaccordance with the present disclosure;

FIG. 2A is a perspective view of an end effector assembly provided inaccordance with the present disclosure and configured for use witheither of the surgical instruments of FIGS. 1A and 1B, wherein jawmembers of the end effector assembly are disposed in a spaced-apartposition;

FIG. 2B is a perspective view of the end effector assembly of FIG. 2A,wherein the jaw members of the end effector assembly are disposed in anapproximated position;

FIG. 3 is a side view of another end effector assembly provided inaccordance with the present disclosure and configured for use witheither of the surgical instruments of FIGS. 1A and 1B;

FIG. 4 is a longitudinal, cross-sectional view of the jaw members ofanother end effector assembly provided in accordance with the presentdisclosure; and

FIG. 5 is a schematic illustration of a generator provided in accordancewith the present disclosure and configured for use with any of the endeffector assemblies provided herein or any other suitable end effectorassembly.

DETAILED DESCRIPTION

The present disclosure relates generally to surgical devices and methodsfor applying energy, e.g., RF energy, to bowel (intestine) tissue orother similar tissue structures to treat, e.g., seal, tissue. Referringto FIG. 1A, a surgical forceps 10 is depicted. For the purposes herein,either surgical forceps 10, or any other suitable surgical instrumentmay be utilized in accordance with the present disclosure. Obviously,different connections and considerations apply to each particular typeof instrument; however, the aspects and features of the presentdisclosure with respect to sealing bowel tissue or other similar tissuestructures remains generally consistent with respect to any suitableinstrument.

Continuing with reference to FIG. 1A, forceps 10 includes a shaft 12, ahousing 20, a handle assembly 22, a trigger assembly 25, a rotatingassembly 28, and an end effector assembly 100. Shaft 12 has a distal end16 configured to mechanically engage end effector assembly 100 and aproximal end 14 that mechanically engages housing 20. A cable 34 couplesforceps 10 to an energy source, e.g., an RF generator 40, fortransmitting energy and control signals between generator 40 and forceps10. Cable 34 houses a plurality of wires 56 that are internally dividedwithin handle assembly 22 and/or in shaft 12 into wires 56 a-56 c, whichelectrically interconnect end effector assembly 100, activation switch30, and/or generator 40 with one another. Generator 40 is described ingreater detail below.

With continued reference to FIG. 1A, handle assembly 22 includes amovable handle 24 and a fixed handle 26. Fixed handle 26 is integrallyassociated with housing 20 and movable handle 24 is movable relative tofixed handle 26. Movable handle 24 is ultimately connected to a driveassembly (not shown) that, together, mechanically cooperate to impartmovement of jaw members 110, 120 of end effector assembly 100 between aspaced-apart position and an approximated position to grasp tissuetherebetween. As shown in FIG. 1A, movable handle 24 is initiallyspaced-apart from fixed handle 26 and, correspondingly, jaw members 110,120 are disposed in the spaced-apart position. Movable handle 24 ismovable from this initial position to one or more compressed positionscorresponding to one or more approximated positions of jaw members 110,120 (see FIG. 2B). A latching assembly 27 may be provided forselectively locking movable handle 24 relative to fixed handle 26 atvarious positions between the initial position and the compressedposition(s) to lock jaw members 110, 120 at various different positionsduring pivoting, e.g., the one or more approximated positions. Rotatingassembly 28 is rotatable in either direction to similarly rotate endeffector assembly 100 relative to shaft 12.

End effector assembly 100 is shown attached at the distal end 16 ofshaft 12 and includes opposing jaw members 110 and 120. Each jaw member110, 120 includes an electrically-conductive tissue-contacting surface112, 122, respectively, that cooperate to grasp tissue therebetween andseal grasped tissue upon application of energy from generator 40. Morespecifically, tissue-contacting surfaces 112, 122 are electricallycoupled to generator 40, e.g., via wires 56 a, 56 b, and are configuredto conduct RF energy provided by generator 40 between tissue-contactingsurfaces 112, 122 and through tissue grasped therebetween to treat,e.g., seal, tissue. Other suitable forms of energy, e.g., thermal,microwave, light, ultrasonic, etc., are also contemplated. Either orboth jaw members 110, 120 may further include one or more non-conductivestop members 124 (FIG. 2A) disposed on the tissue-contacting surface112, 122 thereof to define a minimum gap distance betweentissue-contacting surfaces 112, 122 when jaw members 110, 120 aredisposed in a fully approximated position.

An activation switch 30 is disposed on housing 20 and is coupled betweengenerator 40 and tissue-contacting surfaces 112, 122 via wire 56 c.Activation switch 30 is selectively activatable to provide energy fromgenerator 40 to tissue-contacting surface 112 of jaw member 110 (and/ortissue-contacting surface 122 of jaw member 120) of end effectorassembly 100. More specifically, when activation switch 30 is depressed,a resistance drop across circuitry 32 is recognized by generator 40 toinitiate electrosurgical energy to supply a first electrical potentialto jaw member 110 and a second electrical potential to jaw member 120.

End effector assembly 100 is designed as a bilateral assembly, i.e.,wherein both jaw member 110 and jaw member 120 are movable about a pivot19 relative to one another and to shaft 12. However, end effectorassembly 100 may alternatively be configured as a unilateral assembly,i.e., wherein one of the jaw members, e.g., jaw member 120, is fixedrelative to shaft 12 and the other jaw member, e.g., jaw member 110, ismovable about pivot 19 relative to shaft 12 and the fixed jaw member120.

In some embodiments, a knife assembly (not shown) is disposed withinshaft 12 and a knife channel 115 is defined within one or both jawmembers 110, 120 to permit reciprocation of a knife blade (not shown)therethrough, e.g., via actuation of trigger assembly 25, to cut tissuegrasped between jaw members 110, 120. Alternatively or additionally, endeffector assembly 100 may be configured for energy-based tissue cutting.

Referring to FIG. 1B, a cordless, or battery-powered forceps 10′ isshown including an internal energy source 50, e.g., for generating RFenergy or any other suitable form of energy (such as thermal, microwave,light, ultrasonic, etc.), disposed within housing 20′. Internal energysource 50 is operably coupled to a battery compartment 52 disposedwithin fixed handle 26′ via one or more wires 56′. Battery compartment52 is adapted to receive one or more batteries 54 for providing suitableenergy to internal energy source 50. Internal energy source 50 providesRF energy to end effector assembly 100 via one or more wires 56′ and isalso coupled to activation switch 30′ via one or more wires 56′ forallowing the selective application of energy from internal energy source50 to end effector assembly 100, similarly as detailed above. Forceps10′ may otherwise be configured similar to forceps 10 (FIG. 1A),discussed above.

Turning now to FIGS. 2A-2B, in conjunction with FIG. 1A, an end effectorassembly 100 configured for use with either forceps 10 (FIG. 1A),forceps 10′ (FIG. 1B), or any other suitable surgical instrument isshown. End effector assembly 100, as mentioned above, includes a pair ofopposing jaw members 110 and 120, each having an electrically-conductivetissue-contacting surface 112, 122, respectively, disposed thereon. Jawmembers 110, 120 are movable between a spaced-apart position (FIG. 2A)and an approximated position (FIG. 2B) to grasp tissue betweentissue-contacting surfaces 112, 122. When disposed in the approximatedposition (FIG. 2B), jaw members 110, 120 are configured to impart aspecific clamping pressure (or clamping pressure within a specificclamping pressure range) to tissue grasped between jaw members 110, 120.More specifically, with additional reference to FIG. 1A, handle assembly22 and/or latching assembly 27, in conjunction with the drive assembly(not shown), may be configured to impart the specific clamping pressure(or clamping pressure within a specific clamping pressure range) totissue grasped between jaw members 110, 120. This may be achievedmanually, e.g., via the user moving movable handle 24 from the initialposition to a specific compressed position (or positions), viamechanical latching, e.g., wherein latch assembly 27 is configured tolatch jaw members 110, 120 in a specific position (or positions), viafeedback-based control (automatic or manual), or via any other suitablemechanism or feature. Suitable mechanisms for this purpose include thosedescribed in U.S. Pat. Nos. 5,776,130; 7,766,910; 7,771,426; and8,226,650; and/or U.S. Patent Application Pub. Nos. 2009/0292283;2012/0172873; and 2012/0184988, the entire contents of all of which arehereby incorporated by reference herein. Other suitable mechanisms forapplying a specific clamping pressure (or clamping pressure within aspecific clamping pressure range) to tissue grasped between jaw members110, 120 may also be provided.

With tissue grasped between jaw members 110, 120 under the specificclamping pressure (or clamping pressure within a specific clampingpressure range), energy may be supplied to either or bothtissue-contacting surfaces 112, 122 of jaw members 110, 120,respectively, to seal tissue. The particular sealing parameters providedin accordance with the present disclosure that have been found to beparticularly applicable for use in sealing bowel tissue or other similartissue structures are detailed below.

Turning now to FIG. 3, another embodiment of an end effector assemblyconfigured for use with forceps 10 (FIG. 1A), forceps 10′ (FIG. 1B), orany other suitable surgical instrument is shown and generally identifiedas end effector assembly 200. Similar to end effector assembly 100(FIGS. 2A-2B), end effector assembly 200 includes first and second jawsmembers 210, 220, each including an opposed electrically-conductivetissue-contacting surface 212, 222 adapted to connect to a source ofenergy, e.g., generator 40 (FIG. 1A), for conducting energy betweentissue-contacting surfaces 212, 222 and through tissue graspedtherebetween to treat, e.g., seal, tissue. However, rather thanproviding pivotable jaw members, jaw members 210, 220 of end effectorassembly 200 are linearly movable between a spaced-apart position andone or more approximated positions for grasping tissue therebetween. Asshown, jaw member 210 is fixed relative to shaft 202, while jaw member220 is coupled to a drive member 204 that is selectively translatablethrough and relative to shaft 202, e.g., via actuation of handleassembly 22 (FIG. 1A), to move jaw member 220 relative to jaw member 210between the spaced-apart position and one or more approximatedpositions. Alternatively, end effector assembly 200 may be configured asa bilateral assembly, wherein both jaw members 210, 220 are movablerelative to one another. In either configuration, tissue-contactingsurfaces 212, 222 of jaw members 210, 220 are maintained in parallelorientation relative to one another regardless of the relativepositioning therebetween, thus helping to ensure application of auniform closure pressure tissue grasped therebetween. Other suitable endeffector assemblies configured to provide parallel closure of thetissue-contacting surfaces and suitable for use in accordance with thepresent disclosure include, for example, the end effector assembliesdisclosed in U.S. Pat. No. 5,190,541 and U.S. Patent Application Pub.No. 2010/0057084, the entire contents of each of which is herebyincorporated by reference herein.

FIG. 4 illustrates another end effector assembly provided in accordancewith the present disclosure, shown generally identified by referencenumeral 300. End effector assembly is similar to end effector assembly100 (FIGS. 2A-2B) and may include any of the features of end effectorassembly 100 (FIGS. 2A-2B) or any of the other end effector assembliesdetailed herein, and vice versa. End effector assembly 300 includesfirst and second jaw members 310, 320 each including anelectrically-conductive tissue-contacting surface 312, 322,respectively. Jaw members 310, 320 are movable between a spaced-apartposition and one or more approximated positions to grasp tissue betweentissue-contacting surfaces 312, 322. Wires 314, 324 electrically coupletissue-contacting surfaces 312, 322 to a source of energy, e.g.,generator 400 (FIG. 5), for conducting RF energy betweentissue-contacting surfaces 312, 322 and through tissue graspedtherebetween to treat, e.g., seal, tissue.

Either or both jaw members 310, 320 of end effector assembly 300 mayfurther include a sensor 316, 326 positioned adjacent the respectivetissue-contacting surface 312, 322 and configured to sense one or moreparameters, e.g., tissue impedance, tissue temperature, current and/orvoltage applied to tissue, etc., and/or one or more tissue properties,e.g., optical tissue properties, physical tissue properties, etc.Sensors 316, 326 are coupled to the source of energy, e.g., generator400 (FIG. 5), via wires 318, 328 to provide feedback and/or enablefeedback-based control, as will be described in greater detail below.

FIG. 5 shows a schematic block diagram of a generator 400 which may beutilized as a stand-alone generator, similar to generator 40 (FIG. 1), agenerator incorporated into a surgical instrument, similar to generator50 (FIG. 1B), or any other suitable generator. Generator 400 includessensor circuitry 422, a controller 424, a high voltage DC power supply(“HVPS”) 427 and an RF output stage 428. HVPS 427 provides high voltageDC power to RF output stage 428 which converts the high voltage DC powerinto RF energy for delivery to the end effector assembly, e.g.,tissue-contacting surfaces 312, 322 of jaw members 310, 320,respectively, of end effector assembly 300 (FIG. 4). In particular, RFoutput stage 428 generates sinusoidal waveforms of high frequency RFenergy. RF output stage 428 is configured to generate a plurality ofwaveforms having various duty cycles, peak voltages, crest factors, andother parameters, depending on a particular mode of operation.

Controller 424 includes a microprocessor 425 operably connected to amemory 426 which may be volatile type memory (e.g., RAM) and/ornon-volatile type memory (e.g., flash media, disk media, etc.).Microprocessor 425 is operably connected to HVPS 427 and/or RF outputstage 428 allowing microprocessor 425 to control the output of generator400, e.g., in accordance with feedback received from sensor circuitry422. Sensor circuitry 422 is operably coupled to wires 314, 324, whichprovide and return energy to/from tissue-contacting surfaces 312, 322(FIG. 4), and/or wires 318, 328, which provide the sensed parametersfrom sensors 316, 326 of jaw members 310, 320 (see FIG. 4), to establishfeedback control of the output of generator 400. From wires 314, 324,sensor circuitry 422 may determine one or more parameters, e.g., tissueimpedance, output current and/or voltage, etc., while wires 318, 328provide one or more of parameters or tissue properties, such as thosenoted above, or other suitable sensed parameters or tissue properties.Sensor circuitry 422 provides feedback based upon the sensedparameter(s) and/or tissue property(s) to controller 424 which, in turn,signals HVPS 427 and/or RF output stage 428 to adjust the DC and/or RFpower supply accordingly.

With respect to controlling the output of generator 400 based upontissue impedance, as mentioned above, tissue impedance can be monitoredvia sensor circuitry 22. More specifically, tissue impedance can bemonitored relative to a target end impedance, e.g., the peak relativeincrease in impedance from a baseline value, while the monitored tissueimpedances values can also be utilized to determine an impedance ramp,e.g., the rate of increase/decrease of tissue impedance as a function oftime, as compared to a target impedance ramp. Depending on theparticular target values set (and stored in memory 426, for example),microprocessor 425 may accordingly provide for automatic adjustment orcontrol of the power and/or energy output of generator 400. A clock (notshown) may also be provided for controlling sealing time (the amount oftime energy is supplied to tissue), in conjunction with theabove-described impedance control. Impedance and/or sealing time controlmay be utilized to inhibit tissue denaturation, damage, tissue layerarchitecture breakdown, etc. A specific implementation of impedancefeedback-based control particularly suited for sealing bowel tissue orother similar tissue structures is detailed below.

With respect to controlling the output of generator 400 based uponoptical tissue properties, sensors 316, 318 (FIG. 4) may be configuredas optical sensors configured to sense one or more optical properties oftissue and provide the same to sensor circuitry 422. Such opticalsensors (or other suitable sensors) may be utilized to sense changes inthe collagen matrix of tissue, denaturation of tissue, tissue damage,tissue layer architecture breakdown, and/or other suitable tissueproperties. Microprocessor 425 may accordingly provide for automaticadjustment or control of the power and/or energy output of generator 400based upon this sensed feedback, e.g., to inhibit denaturation, damage,tissue layer architecture breakdown, etc. Temperature-based feedback mayadditionally or alternatively be utilized to ensure tissue issufficiently heated while also maintaining tissue at a temperature belowthe temperature at which denaturation, damage, tissue layer architecturebreakdown, etc. occurs.

Any of the above-detailed end effector assemblies, instruments, andsystems, may also be configured to work with robotic surgical systemsand what is commonly referred to as “telesurgery.” Such robotic systemsemploy various robotic elements to assist the surgeon in the operatingtheater and allow remote operation (or partial remote operation) of theend effector assembly and surgical instrumentation. Various roboticarms, gears, cams, pulleys, electric and mechanical motors, etc. may beemployed for this purpose and may be designed with a robotic surgicalsystem to assist the surgeon during the course of an operation ortreatment. Such robotic systems may include remotely steerable systems,automatically flexible surgical systems, remotely flexible surgicalsystems, remotely articulating surgical systems, wireless surgicalsystems, modular or selectively configurable remotely operated surgicalsystems, etc.

The robotic surgical systems may be employed with one or more consolesthat are next to the operating theater or located in a remote location.In this instance, one team of surgeons or nurses may prep the patientfor surgery and configure the robotic surgical system with surgicalinstrumentation and/or an end effector assembly, e.g., any of thosedisclosed hereinabove, while another surgeon (or group of surgeons)remotely controls the end effector assembly and/or other instrumentationvia the robotic surgical system. As can be appreciated, a highly skilledsurgeon may perform multiple operations in multiple locations withoutleaving his/her remote console which can be both economicallyadvantageous and a benefit to the patient or a series of patients.

The robotic arms of the surgical system are typically coupled to a pairof master handles by a controller. The handles can be moved by thesurgeon to produce corresponding movement, manipulation, and/oractuation of the end effector assembly, e.g., to position the endeffector assembly, grasp tissue, supply energy to tissue, deploy a knifefor cutting tissue, release tissue, etc. The master handles may includevarious sensors to provide feedback to the surgeon relating to varioustissue parameters or conditions, e.g., tissue resistance due tomanipulation, cutting or otherwise treating, pressure by the instrumentonto the tissue, tissue temperature, tissue impedance, etc. As can beappreciated, such sensors provide the surgeon with enhanced tactilefeedback simulating actual operating conditions. These sensors andfeedback systems may be incorporated into and/or work in conjunctionwith the sensors and feedback systems of the instruments, end effectorassemblies, and/or generators detailed hereinabove. The master handlesmay further include a variety of different actuators for delicate tissuemanipulation or treatment to further enhancing the surgeon's ability tomimic actual operating conditions.

Sealing bowel tissue and other similar tissue structures has been foundto require different sealing parameters, e.g., clamping pressure, gapdistance, and/or energy control, as compared to sealing blood vessels,vascular tissue, and the like, due to differences in tissue compositionand structure as well as differences in the physiological utilizationsof these tissues. More specifically, bowel tissue is thicker and moremuscular tissue as compared to blood vessels and vascular tissue. Boweltissue is also more sensitive and is required to maintain function aftersealing to fulfill its role in the digestive and excretory processes. Asa result of the particular composition and functions of bowel tissue, abalance must be struck between the interest of ensuring formation of anadequate seal and the competing interest of minimizing denaturation,damage, tissue layer architecture breakdown, etc. of the tissue (whichis typically not a concern with regard to sealing blood vessels andvascular tissues). It is contemplated that the above-describedmechanisms, instruments, systems, end effector assemblies, generators,etc., alone or in combination with one another, be utilized to sealbowel tissue in accordance with these considerations, as described indetail below.

Taking into account the above-identified considerations, it has beenfound that a clamping pressure in the range of about 1 kg/cm² to about2.5 kg/cm² applies sufficient pressure to bowel tissue to enableformation of an adequate bowel seal through merging of tissue layers,while also inhibiting/minimizing denaturation, damage, tissue layerarchitecture breakdown, etc. That is, bowel tissue seals have been foundto be inadequate when formed using clamping pressures below about 1kg/cm², while the level of tissue denaturation, damage, overall tissuelayer architecture breakdown, etc. has been found to negatively effectthe viability and/or performance of the sealed bowel tissue when formedusing clamping pressures above 2.5 kg/cm². During sealing, the clampingpressure may be regulated and maintained within this clamping pressurerange via use of any of the mechanisms detailed above or described inU.S. Pat. Nos. 5,776,130; 7,766,910; 7,771,426; and 8,226,650; and/orU.S. Patent Application Pub. Nos. 2009/0292283; 2012/0172873; and2012/0184988, previously incorporated by reference herein, or via anyother suitable methods or mechanisms.

With respect to gap distance, any suitable gap distance (constant orvaried) between the tissue-contacting surfaces of the jaw members may beused during the sealing cycle so as to regulate and/or maintain theclamping pressure within the above-identified clamping pressure rangethroughout a portion of or the entire sealing cycle. The gap distancemay likewise be maintained via use of any of the mechanisms detailedabove or those described in U.S. Pat. Nos. 5,776,130; 7,766,910;7,771,426; and 8,226,650; and/or U.S. Patent Application Pub. Nos.2009/0292283; 2012/0172873; and 2012/0184988, previously incorporated byreference herein, or via any other suitable methods or mechanisms.

With respect to energy control, it has been found that an effectivebowel seal, using a clamping pressure within the range of about 1 kg/cm²to about 2.5 kg/cm², can be established via temperature feedback-basedenergy control, optical tissue property feedback-based energy control,and/or impedance feedback-based energy control, e.g., using a feedbackbased system such as that detailed above with respect to end effectorassembly 300 (FIG. 4) and generator 400 (FIG. 5).

Temperature control may be utilized to adjust the energy output suchthat tissue is sufficiently heated to enable formation of an effectivetissue seal, but is maintained at a temperature below the temperature atwhich denaturation, damage, tissue layer architecture breakdown, etc.occurs.

Impedance control can be implemented to adjust the energy output using atarget end impedance of about 200Ω and a target impedance ramp of about0.010 Ω/ms, so as to ensure that the tissue is adequately sealed withoutdamaging or negatively altering the tissue. Further, suchimpedance-control provides for a sealing cycle time typically in therange of about 18 to 22 seconds and, thus, tissue sealing time can alsobe utilized as feedback parameter.

Optical tissue property control may be utilized, as mentioned above, toadjust the energy output to inhibit denaturation, damage, breakdown oftissue layer architecture, etc. during the tissue sealing cycle bymonitoring one or more properties or indications of such, e.g., changesin the collagen matrix of tissue, denaturation of tissue, changes intissue layer architecture, etc.

While several embodiments of the disclosure have been shown in thedrawings and/or discussed herein, it is not intended that the disclosurebe limited thereto, as it is intended that the disclosure be as broad inscope as the art will allow and that the specification be read likewise.Therefore, the above description should not be construed as limiting,but merely as exemplifications of particular embodiments. Those skilledin the art will envision other modifications within the scope and spiritof the claims appended hereto.

What is claimed is:
 1. A method of sealing tissue, comprising: providinga target impedance ramp, wherein the target impedance ramp represents achange in impedance as a function of time that results in sealing oftissue while minimizing tissue denaturation, tissue damage, andbreakdown of tissue layer architecture; grasping tissue between firstand second electrically-conductive surfaces; sealing the grasped tissueby supplying energy to at least one of the first and secondelectrically-conductive surfaces such that the energy is conductedbetween the first and second electrically-conductive surfaces andthrough the grasped tissue; monitoring an impedance of the graspedtissue as a function of time during the supplying of energy to the atleast one of the first and second electrically-conductive surfaces;determining an actual impedance ramp, wherein the actual impedance ramprepresents the monitored impedance of the grasped tissue as a functionof time; and controlling the supply of energy to the at least one of thefirst and second electrically-conductive surfaces based on a comparisonof the actual impedance ramp with the target impedance ramp to maintainthe actual impedance ramp equal to the target impedance ramp such thatthe grasped tissue is sealed with minimal tissue denaturation, tissuedamage, and breakdown of tissue layer architecture of the grasped tissuethat is being sealed to maintain viability of the tissue that is beingsealed.
 2. The method according to claim 1, wherein the target impedanceramp is about 0.010 Ω/ms.
 3. The method according to claim 1, whereinsupplying energy to the at least one of the first and secondelectrically-conductive surfaces includes supplying energy until tissueimpedance reaches a target end impedance.
 4. The method according toclaim 3, wherein the target end impedance is about 200 Ω.
 5. The methodaccording to claim 1, wherein the tissue is bowel tissue.
 6. A method ofsealing tissue, comprising: providing a lower tissue temperature limitcorresponding to a minimum temperature for sealing tissue; providing anupper tissue temperature limit corresponding to a maximum temperatureprior to occurrence of tissue denaturation, tissue damage, and breakdownof tissue layer architecture; grasping tissue between first and secondelectrically-conductive surfaces; sealing the grasped tissue bysupplying energy to at least one of the first and secondelectrically-conductive surfaces such that the energy is conductedbetween the first and second electrically-conductive surfaces andthrough the grasped tissue; monitoring a temperature of the graspedtissue during the supplying of energy to the at least one of the firstand second electrically-conductive surfaces; determining an actualtissue temperature, wherein the actual tissue temperature represents themonitored temperature of the grasped tissue; controlling the supply ofenergy to the at least one of the first and secondelectrically-conductive surfaces based on a comparison of the actualtissue temperature of the grasped tissue with the lower and uppertemperature limits; and maintaining the actual tissue temperature of thegrasped tissue between the lower temperature limit and the uppertemperature limit, such that the grasped tissue is sealed with minimaltissue denaturation, tissue damage, and breakdown of tissue layerarchitecture of the grasped tissue that is being sealed to maintainviability of the tissue that is being sealed.
 7. The method according toclaim 6, wherein the tissue is bowel tissue.